This application is based on application No. 2001-328842 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electron gun and a cathode-ray tube, in particular to a technology of shortening a length of the electron gun.
2. Related Art
In recent years, flat display devices such as PDPs (Plasma display panel) and LCD displays have been remarkably prevailed. Accordingly, it is being required to reduce the depth of a cathode-ray tube apparatus used therefor. To solve the mentioned problem, there has been already an attempt to improve a deflection yolk so as to enlarge a deflection angle of the electron beam.
In addition, a technology has been considered to downsize the electron gun, which will lead to downsizing of the length of the cathode-ray tube apparatus. Examples thereof include a structure of the electron gun disclosed in a Japanese Laid-open Patent Application No. H02-056836. Normally, the cathode of the electron gun, the control electrode, and the accelerating electrode are independently fixed to the multi-form glass rod. Whereas the technology disclosed in this patent application fixes these electrodes altogether to the multi-form glass rod, in an attempt to reduce the size of the electron gun. Hereinafter, electrodes that are made up of a cathode of the electron gun, the control electrode, and the accelerating electrode are collectively referred to as xe2x80x9cthree-electrode part.xe2x80x9d
FIG. 1 is a sectional diagram showing a structure of the three-electrode part as disclosed in the Japanese Laid-open Patent Application No. H02-056836. The three-electrode part relating to this patent application is made up of a thermal cathode 101, a control electrode 106, and an accelerating electrode 108. A heater 102 that heats the thermal cathode 101 has a long structure in the direction of the tube-axis, whose longitudinal length is approximately 3-5 mm.
The heater 102 is surrounded by a sleeve 103 that is in a tubular form. The sleeve 103 is in turn surrounded and supported by a bush 104, which is also in a tubular form. The bush 104 is fit by insertion to the cathode support 105. Further, the control electrode 106 is provided at a place where it is closer to the screen than the cathode support 105 in a tube-axis direction. An electrically non-conductive spacer 107 is provided at a place where it is closer to the screen than the control electrode 106 in a tube-axis direction.
The accelerating electrode 108 is in a form of a cup. The electrically non-conductive spacer 107, the control electrode 106, and cathode support 105 are arranged to be stored inside the accelerating electrode 108, in this order from the bottom of the accelerating electrode 108. The mentioned members are fixed inside the accelerating electrode 108 by the electrode-pressing member 109 fit by insertion to the accelerating electrode 108.
Here, the heater is supported by a heater supporting hardware 110 inside the sleeve 103, in such a manner that the heater is not in direct contact with the sleeve 103. Structured in the above way, it is possible to keep accurate distances between the electrodes making up the three-electrode part, which helps reducing the size of the length of the electron gun.
However, the length of the electron gun which is from the heater supporting hardware 110 to the accelerating electrode 108 is about 12-20 mm. Further reduction in size of the electron gun is desired for reducing the length of the entire cathode-ray tube apparatus.
The object of the present invention, in view of the above-described problems, is to provide an electron gun having a reduced length in the direction of the tube-axis, and further to provide a cathode-ray tube apparatus, which includes such electron gun.
In order to solve the stated problems, an electron gun relating to the present invention is characterized by including: an electrically non-conductive member through which a perforation is provided; a cathode structure which is made up of a thermal cathode and a heater; a plurality of power-feeding members that are provided on a side of the electrically non-conductive member, the side being opposite to a side from which the cathode structure emits electron beams; a first cathode-structure supporting member that electrically connects the heater with at least two of the power-feeding members and supports the cathode structure; and a second cathode-structure supporting member that electrically connects the thermal cathode with at least one of the power-feeding members and supports the cathode structure.
Structured in such a way, the cathode structure including the heater and the thermal cathode is supported by the electrically non-conductive member, through the first and second cathode-structure supporting members, the heater being a part of the cathode structure. Therefore, it becomes unnecessary to have such member as the heater supporting hardware 110, thereby reducing an entire length of the electron gun. In addition, the first and second cathode-structure supporting members are used to supply power to the thermal cathode and to the heater, the power having come from the power-feeding members. This even more helps to realize a compact electron gun.
Furthermore, according to the above structure, the distance between the control electrode and the cathode structure is able to be adjusted, in mounting the first and second cathode-structure supporting members to the power-feeding members, where the first and second cathode-structure supporting members have been already mounted to the cathode structure. This makes it possible to realize an electron gun that can be assembled with accuracy. Moreover, the yield factor is improved for producing such electron gun.
In addition, according to the structure, it is possible to cut the first and second cathode-structure supporting members, so as to take out the cathode structure. This facilitates taking the parts apart, thereby promoting recycling use of such parts.
Further, the cathode-ray tube apparatus of the present invention is characterized by a cathode-ray tube apparatus including an electron gun that has: an electrically non-conductive member through which a perforation is provided; a cathode structure which is made up of a thermal cathode and a heater; a plurality of power-feeding members that are provided on a side of the electrically non-conductive member, the side being opposite to a side from which the cathode structure emits electron beams; a first cathode-structure supporting member that electrically connects the heater with at least two of the power-feeding members and supports the cathode structure; and a second cathode-structure supporting member that electrically connects the thermal cathode with at least one of the power-feeding members and supports the cathode structure.